Disclaimer: I am not affiliated with Undercover Tourist, but I have used, and recommended their services before.
This is a good overview regarding FP+ and MM+. It answers many of the questions that seem to float around the internet quite often. It can be a bit confusing, and even a bit frustrating at times, especially when comparing how it was done in the past, but it with a bit of prepwork, it does work.
My biggest tip for getting FastPasses is try to get times that are close to each other. This way, you can hit attractions in rapid succession and then have more options during the other parts of the day. This is a bit more difficult to do if you are trying to do different dining reservations during the day, but I found that grouping things closer, either in the morning or afternoon, helps keep the fun moving along. You may not be able to do this sort of grouping all the time due to your plans or FP availability, but it is something to consider.
Have a great one!